A so-called pathological diagnosis is widely conducted, in which a tissue slice taken from a living body such as a human being or an animal is observed with a microscope to diagnose presence or absence of a lesion, a type of the lesion, and the like. In this pathological diagnosis, the tissue slice to be diagnosed is generally presented to microscope observation after being subjected to fixation, embedding, slicing, and staining sequentially in this order.
In recent years, a microscope observation technology has been provided, in which an image (also referred to as a “cell morphological image”) capturing a shape of a biological tissue containing a plurality of cells is acquired, and the shape of the cell is automatically extracted from the cell morphological image through image processing (for example, see Patent Literatures 1 to 4).
For example, in Patent Literature 1, a pixel group serving as a candidate for a cell center is extracted from the cell morphological image, and only pixels suitable for the cell center in the pixel group are selected on the basis of a predetermined criterion. In addition, pixels that form an outline of the cell are selected based on position information of the selected cell center pixels and a concentration gradient direction of its neighboring pixels.
In Patent Literature 2, at least one of a point having a minimum or a maximum luminance, a point having a color different from those of the surrounding points, and a point having a maximum luminance gradient is extracted as an extraction point from the cell morphological image, and clustering for the extraction point is performed to determine the center and boundary of the cell.
In Patent Literature 3, pixels sorted on the basis of an attribute value range are added to a label image one by one from an end point of the attribute value range. In addition, when the feature calculated for each arranged object meets a predetermined allowable criterion, the object is output as an output image. In this case, each object in the image is identified by repeating addition of the pixels to the label image, evaluation of the feature of the created object, and output of the object until the stop point.
In Patent Literature 4, a group of cells having the feature similar to that of a specific cell of interest specified by a user are automatically extracted from a plurality of cells of the cell morphological image subjected to a predetermined processing.